PROJECT SUMMARY Magnesium levels modulate the activity of enzymes involved in glycolysis, the Krebs cycle, and the respira- tory chain; thus have the potential to influence the metabolic transformation required for increased cell prolifer- ation and invasiveness in cancer. The role of magnesium homeostasis in cancer, however, has remained un- derexplored, mainly due to the paucity of efficient tools for the detection of Mg2+ in cells without interference from other biologically?relevant metals. For example, the prostate gland accumulates high levels of divalent cations such as Mg2+, Zn2+ and Ca2+, which are secreted with citrate as part of the prostatic fluid and are re- quired for proper gland function. Disruption of metal homeostasis has been proposed to be intimately involved in the metabolic shift from citrate production to citrate oxidation that precedes the neoplastic stage in the de- velopment of prostate malignancies. Whereas much progress has been made on elucidating the role of other divalent cations in this process, the role of magnesium in the etiology of prostate cancer is still a mystery. In this proposal, we seek to optimize molecular probes for selective visualization and quantification of magnesium in samples with high levels of interfering metals, and to capitalize on the new tools to establish the patterns of magnesium accumulation in prostate cells and tissue in relationship with metabolic activity and disease pro- gression. These studies represent a critical first step toward obtaining a complete picture of the metallome of the prostate gland and establishing the possible role of Mg2+ cations in the metabolic reprogramming associat- ed with cancer. The specific aims of the project include (i) to develop optimal molecular probes for visualization and quantification of intracellular Mg2+ in tissues with high levels of interfering metals; (ii) to map the distribution of Mg2+ and other divalent metal cations in prostate tissue samples representative of different stages of pros- tate malignancy; and (iii) to study the correlation between cellular Mg2+ uptake with metabolic activity in cancer cells. These studies will offer new insight into the role of Mg2+ as a new, thus far unexplored factor influencing the metabolic transformation occurring in early stages of PCa. Deeper understanding of the connection be- tween magnesium homeostasis and cancer progression may lead to the identification of new therapeutic tar- gets centered in cation transport, and open the door to the use of metal levels as biomarkers for the develop- ment of novel diagnostic and surveillance tools for PCa and other cancers.